Ingo Klaucke¹, Reinhard Hesse², W.B.F. Ryan³
(1) Southampton Oceanography Centre, Southampton, United Kingdom
(2) McGill University, Montreal, QC
(3) Lamont-Doherty Earth Observatory, Palisades, NY

Abstract: Growth pattern of a mid-ocean channel-levee complex based on 3D sleeve-gun seismic profiles, northwest Atlantic mid-ocean channel (NAMOC), Labrador Sea

Seismic stratigraphic analysis of closely spaced 40 in3 sleeve-gun profiles from the highly asymmetric levees (250 m thick western and 150 m thick eastern levee) of the proximal NAMOC reveals seven stages of levee formation that are characterized by traceable packages of low-amplitude reflections separated by a few high-amplitude reflections, except for the second-last stage, which shows high-amplitude reflections throughout. The southeastward prograding, well-correlated levee stages overlie a seismic facies of discontinuous high-amplitude reflections that probably represents channel-fill under the channel and submarine braidplain deposits under the outer levees. The NAMOC levees have grown since the mid-Pleistocene by spill-over deposition from turbidity currents under the influence of the Coriolis force. This resulted in increasing levee height and asymmetry with time as deposition in the channel raised the channel floor to equilibrium depth. The degree of levee asymmetry changes as a function of inferred turbidity-current velocity within the channel. The latest stage of levee construction has symmetric levees, because increasing levee height altered the spill-over mechanism from continuous flow-stripping of the top of turbidity currents to diffusion perpendicular to the channel from sediment clouds arising from currents passing through the channel.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana